This is "outside the box" compared to traditional alarm concepts, but
what about active sensors with the 1-wire protocol?

(for anybody not up to speed, 1-wire actually uses 2 wires, ground and
signal/power. Power is parasitically 'stolen' from the signal line.
Many sensors can reside on the same data bus and they are identified
by unique electronic serial numbers. Data / info / sample parts can be
obtained through the Dallas / Maxim web site www.maxim-ic.com )

With an active data protocol, it would be extremely secure (almost
impossible to bypass) and you'd be able to pass much more information
than a simple current loop.


BTW, I don't know what kind of class you're in, or what kind of
diploma your trying to achieve, but in my classes a two wire current
loop alarm would not have made the grade unless there was something
really unique about it somewhere.

-Denny



----- Original Message -----
From: "Lucian" <lucicop@GO.RO>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Sunday, October 19, 2003 9:00 AM
Subject: [EE:]Supervised Alarm Loop


> Hello,
>
> I am trying to design an alarm system for my diploma project and I
have
> one problem : how should I design a supervised alarm loop in such
way
> that the system can realize when the wire was cut or when the sensor
> connected is in alarm state (those should be two separate states). I
am
> thinking to do it in a 3 wire configuration, one for VCC of the
sensor,
> one for ground and one connected to VCC and in the system to a
window
> comparator, but I'm not sure if it will work or if it is suitable
for a
> security system. Do you think there is a better idea or
configuration
> for an alarm system ?
> Thank you for your help.
>
> Lucian Copat
>
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